Answer:
Theoretical yield of hydrogen is 1.11 g
Explanation:
Balanced equation, 
As Mg remain present in excess therefore HCl is the limiting reagent.
According to balanced equation, 2 moles of HCl produce 1 mol of 
.
Molar mass of HCl = 36.46 g/mol
So, 40.0 g of HCl = 
of HCl = 1.10 moles of HCl
Hence, theoretically, number of moles of are produced from 1.10 moles of HCl = 
Molar mass of = 2.016 g/mol
So, theoretical yield of = 
Answer: During a phase change, such as melting or boiling, the kinetic energy increases.
Explanation:
Kinetic energy is the energy obtained by the molecules of a substance due to their motion.
When phase change such as melting or boiling takes place then it means heat is absorbed by the substance. As a result, their molecules more even more rapidly from one place to another due to which more number of collisions take place.
Hence, a change in phase of substance occurs as kinetic energy increases in melting or boiling process.
Thus, we can conclude that during a phase change, such as melting or boiling, the kinetic energy increases.
Answer:
Rounding for significant figures gives us a final answer of 3.41×1022 atoms 3.41 × 10 22 a t o m s atoms of oxygen.
We can't use the nitrogen present in the atmosphere although 80% of the atmosphere consists of nitrogen only.We get this from the plants called as leguminous plants which can convert or fix atmospheric nitrogen into usable ones..
